Tune up specs
Seasoned HDF Member
Joined: Sep 2012
Posts: 6,570
Likes: 590
From: almost there
Id do 72 main. If I remember right the RPM at 1,500 or a little above.
Put a big fan in front of the engine because if you do the timing light by yourself you will be there a while. The very slightest bump on the ignition will make the mark leave the window. The mark will come into the window ccw.
Put a big fan in front of the engine because if you do the timing light by yourself you will be there a while. The very slightest bump on the ignition will make the mark leave the window. The mark will come into the window ccw.
Seasoned HDF Member
Joined: Mar 2010
Posts: 21,006
Likes: 7,541
From: Poolville
The one thing I missed was in 86 the stock cam that was used had either a 37 degree or 38 degree intake valve closing. The 508 Cam that you are currently running has a 25 degree closing. That's a 12 or 13 degrees difference and it definitely will make a huge difference in dynamic compression.... and on that note if you didn't bump your timing back it is very likely you are getting donation.
Seasoned HDF Member
Joined: Mar 2010
Posts: 21,006
Likes: 7,541
From: Poolville
https://www.savvyanalysis.com/articl...tionDetonation and Pre-Ignition
Mike Bush:"Often confused and misunderstood, these two abnormal combustion phenomena are as different as night and day."
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Tourer
Joined: Dec 2014
Posts: 268
Likes: 69
From: Edgerton Wisconsin
Thanks for all the info guys.
And yes that cam is set up to be real aggressive in the lower rpms. S&s advises against running 10:1 pistons with it because of how much it raises dynamic compression.
I'll throw the timing light on it this weekend and see where I stand, but regardless I'm going to knock it back a few degrees.
Do you think a couple degrees would make enough difference or should I try setting it back 5 and going from there?
And yes that cam is set up to be real aggressive in the lower rpms. S&s advises against running 10:1 pistons with it because of how much it raises dynamic compression.
I'll throw the timing light on it this weekend and see where I stand, but regardless I'm going to knock it back a few degrees.
Do you think a couple degrees would make enough difference or should I try setting it back 5 and going from there?
Seasoned HDF Member
Joined: Mar 2010
Posts: 21,006
Likes: 7,541
From: Poolville
Thanks for all the info guys.
And yes that cam is set up to be real aggressive in the lower rpms. S&s advises against running 10:1 pistons with it because of how much it raises dynamic compression.
I'll throw the timing light on it this weekend and see where I stand, but regardless I'm going to knock it back a few degrees.
Do you think a couple degrees would make enough difference or should I try setting it back 5 and going from there?
And yes that cam is set up to be real aggressive in the lower rpms. S&s advises against running 10:1 pistons with it because of how much it raises dynamic compression.
I'll throw the timing light on it this weekend and see where I stand, but regardless I'm going to knock it back a few degrees.
Do you think a couple degrees would make enough difference or should I try setting it back 5 and going from there?
Thread Starter
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Tourer
Joined: Dec 2014
Posts: 268
Likes: 69
From: Edgerton Wisconsin
So today I put my timing light on my bike and this is what I found. Initially I couldn't find any of the timing marks, so I went ahead and retarded it about 2.5 degrees (one hash mark).
After that I could see the tdc line on the crank at idle (850 rpm). But when I brought the rpms up to between 1500 and 1800 I couldn't for the life of me find the 35 degree dot.
I tried with and without the clear timing plug in and my timing light isnt very bright so maybe I just couldn't see that little dot......
Does 0 degrees at idle mean my baseline is on though?
After that I could see the tdc line on the crank at idle (850 rpm). But when I brought the rpms up to between 1500 and 1800 I couldn't for the life of me find the 35 degree dot.
I tried with and without the clear timing plug in and my timing light isnt very bright so maybe I just couldn't see that little dot......
Does 0 degrees at idle mean my baseline is on though?
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Seasoned HDF Member
Joined: Mar 2010
Posts: 21,006
Likes: 7,541
From: Poolville
Do you have a dial back light. If so, set it to 35* bring the rpm's up to 1200, voes connected and dial in the cam sensor till you see the tdc line and your good to go....
If you don't have a dial back light, at 1200 rpm you should see the 2 dots for the front cylinder. If not confirm adjust the cam sensor till you do.... and as always confirmthat the VOES is working properly.
If you don't have a dial back light, at 1200 rpm you should see the 2 dots for the front cylinder. If not confirm adjust the cam sensor till you do.... and as always confirmthat the VOES is working properly.
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Tourer
Joined: Dec 2014
Posts: 268
Likes: 69
From: Edgerton Wisconsin
Do you have a dial back light. If so, set it to 35* bring the rpm's up to 1200, voes connected and dial in the cam sensor till you see the tdc line and your good to go....
If you don't have a dial back light, at 1200 rpm you should see the 2 dots for the front cylinder. If not confirm adjust the cam sensor till you do.... and as always confirmthat the VOES is working properly.
If you don't have a dial back light, at 1200 rpm you should see the 2 dots for the front cylinder. If not confirm adjust the cam sensor till you do.... and as always confirmthat the VOES is working properly.
I plugged it back in and the 35 degree mark lands right in the center of the hole.
I must have snagged the wire when I was fishing the choke cable down through the dash... The motor felt sluggish but I figured I just didn't have my carb dialed in right yet.
Thank you mmuch for the help!